lose the passengers that are vital to their economic modelling.
Already happening, and they don't seem to care. I dropped from Gold to Silver this year, after stopping flying with them following some lousy customer care incidents. Nothing. No call, no email, no letter asking why.
A few years ago I dropped from EK Gold to Silver (a temporary aberration, I'm Platinum with them these days). Two WEEKS before my membership year ended, I had a manager on the phone, asking me what they had done wrong. Nothing, in effect, my travel plans just didn't fit the EK network at the time, but the fact they bothered, and VS can't be bothered, once more makes me think that VS are heading down the 'we want to be an upmarket Thomas Cook, that's all' route.